Tesco Mobile 4G launches today, for £2.50 extra per month

Tesco Mobile is turning on 4G, for any existing customer that's happy to pay an extra £2.50 per month.

Tesco told me that the new 4G tariffs are open to anyone no matter how old the contract. The deals launch today, hitchhiking on O2's network, so as long as you're happy to pay the extra £2.50, you could be enjoying 4G speeds immediately.

Because O2's network is still new, coverage is limited for now. Over the coming months O2 is bound to add more towns to its 4G roster, however. London, Leeds, Bradford, Birmingham, Coventry, Leicester and Sheffield are currently covered. Today O2 added 4G to Liverpool, but you can check Tesco Mobile's coverage map here for a more detailed look at which areas benefit from speedier data.

Under Tesco's brilliantly-named 'flexi-bendi' tariffs you can turn 4G off if you don't like it. Tesco tells me it won't cost you anything to switch back to 3G. Data limits range from 500MB per month to 8GB.

When you go through the process of starting a Tesco contract online, you'll reach a page asking you whether you want to add a £2.50 charge for the honour of getting extra 4G. The HTC One with 1GB of data, for instance, is free up front and normally costs £32.50 per month, but will set you back £35 if you want 4G.

Tesco Mobile 4G is currently only available for monthly contracts and SIM-only tariffs, but the supermarket says it'll be coming to pay as you go in 2014. Yesterday EE became the first UK network to sell 4G on pay as you go.